refactor(styles): move component-specific CSS into Astro components

- relocate header, footer, nav, hero, and page-hero styles into their owning components
- move blog index, blog post, team, video, insurance, CTA, and home-section styles out of the global sheet
- keep  focused on shared primitives such as buttons, cards, links, and list styling
- preserve existing layout and responsive behavior while reducing global CSS scope

www/src/components/MobileNav.astro

@@ -6,3 +6,10 @@ const { lang = 'en' } = Astro.props;
   <summary>Menu</summary>
   <MainNav lang={lang} />
 </details>
+
+<style>
+  .mobile-nav { display: none; }
+  @media (max-width: 950px) {
+    .mobile-nav { display: block; }
+  }
+</style>